Dynamics of Converging Laser-created Plasmas in Semi-Cylindrical Cavities Studied using Soft X-ray Laser Interferometry

摘要

The evolution of dense aluminum and carbon plasmas produced by laser irradiation of 500 mm diameter semi-cylindrical targets was studied using soft x-ray laser interferometry. Plasmas created heating the cavity walls with 120 picosecond duration optical laser pulses of approximately 1OE1012 W cm-2 peak intensity were observed to expand and converge on axis to form a localized high density plasma region. Electron density maps were measured using a 46.9 nm wavelength tabletop capillary discharge soft x-ray laser probe in combination with an amplitude division interferometer based on diffraction gratings. The measurements show that the plasma density on axis exceeds 1OE1020 cm-3. The electron density profiles are compared with simulations conducted using the hydrodynamic code HYDRA, which show that the abrupt density increase near the axis is dominantly caused by the convergence of plasma generated at the bottom of the groove during laser irradiation.